High-flying birds are able to obtain enough oxygen even when the air is very thin because a. they have more efficient lungs than other vertebrates. b. they have reduced amounts of hemoglobin in their blood. c. their mitochondria are more efficient than those of other vertebrates. and) their heart can increase or decrease in size as altitude changes. e. they are able to store oxygen in oxygen chambers within muscle cells.

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

The largest unit within which gene flow can readily occur is a

Me. henley said, “in the rat race we call life, only the strong will survive.” he may have been referring to